/Engine/Source/Developer/AssetTools/Public/IAssetTools.h
Expands any folders found in the files list, and returns a flattened list of destination paths and files. Mirrors directory structure.
void ExpandDirectories ( const [TArray](API\Runtime\Core\Containers\TArray)< [FString](API\Runtime\Core\Containers\FString) > & Files, const [FString](API\Runtime\Core\Containers\FString) & DestinationPath, [TArray](API\Runtime\Core\Containers\TArray)< TPair< [FString](API\Runtime\Core\Containers\FString), [FString](API\Runtime\Core\Containers\FString) >> & FilesAndDestinations ) const